Founded in 1939 by Huyn Van So, of the village of Hoa Hao, Hoa Hao is an offshoot of Vietnamese Buddhism, which became a religion, social movement, and political force. Theologically, it was an individual religion, without a need for clergy or temples, but its social and political aspects gave it organization.
Early in the Second World War, the Japanese saw it as anti-western, but soon rejected it as nationalist. It then worked with the Viet Minh for a time, but, having gotten arms, split away and formed the Dan Xa Dang political party. So was executed by the Viet Minh in 1947.
In response to the execution, the Hoa Hao then joined the French to fight the Viet Minh, but split off again, and then into individual localities primarily in the Mekong Delta. They supported Bao Dai, which led to its outlawed in 1955 by Ngo Dinh Diem, who executed the most powerful leader; Duong Van Minh led the Diem actions against the Hoa Hao and Cao Dai.
While they were minimized afterwards, they did have some visibility in later Buddhist oppositions, such as the 1965 protest against the High Legislative Council
There remain overseas groups of Hoa Hao.